7.3 Idle channel noise (handset, headset and electrical interface UE)
26.1323GPPRelease 18Speech and video telephony terminal acoustic test specificationTS
7.3.0 Overview
For idle noise measurements in sending and receiving directions, care should be taken that only the noise is windowed out by the analysis and the result is not impaired by any remaining reverberation or by noise and/or interference from various other sources. Some examples are air-conducted or vibration-conducted noise from sources inside or outside the test chamber, disturbances from lights and regulators, mains supply induced noise including grounding issues, test system and system simulator inherent noise as well as radio interference from the UE to test equipment such as ear simulators, microphone amplifiers, etc.
The following steps shall be followed in advance to both measurement directions:
a) The test environment shall comply with the conditions described in subclause 6.1.
b) The terminal should be configured to the test equipment as described in subclause 5.1.
c) A test signal may have to be intermittently applied to prevent ‘silent mode’ operation of the MS. This is for further study.
d) An optional activation sequence may be used, to e.g., override a voice activity detection. In this case, the additional test signal shall be suitable regarding level and bandwidth, like e.g., the composite source signals described in clause 7.10.
To improve repeatability, the test sequence (optional activation followed by the noise level measurement) may be contiguously repeated one or more times.
7.3.1 Sending (handset and headset UE)
In advance to the measurement, the general steps listed in clause 7.3.0 shall be followed.
a) In advance to the noise level measurement, an optional activation sequence may be used.
b) The noise level at the output of the SS is measured with psophometric weighting. The psophometric weighting filter is described in ITU-T Recommendation O.41.
c) The measured part of the noise shall be 170,667 ms (which equals 8192 samples in a 48 kHz sample rate test system). The spectral distribution of the noise is analyzed with an 8k FFT using windowing with ≤ 0,1 dB leakage for non bin-centered signals. This can be achieved with a window function commonly known as a "flat top window". Within the specified frequency range, the FFT bin that has the highest level is searched for; the level of this bin is the maximum level of a single frequency disturbance.
d) The total noise powers obtained from such repeats shall be averaged. The total result shall be 10 * log10 of this average in dB.
e) The single frequency maximum powers obtained from such repeats shall be averaged. The total result shall be 10*log10 of this average in dB.
7.3.2 Receiving (handset and headset UE)
In advance to the measurement, the general steps listed in clause 7.3.0 shall be followed.
a) In advance to the noise level measurement, an optional activation sequence may be used.
b) The noise level shall be measured with A‑weighting at the DRP with diffuse-field correction. The A-weighting filter is described in IEC 61672 [38].
c) The measured part of the noise shall be 170,667 ms (which equals 8192 samples in a 48 kHz sample rate test system). The spectral distribution of the noise is analyzed with an 8k FFT using windowing with ≤ 0.1 dB leakage for non bin-centred signals. This can be achieved with a window function commonly known as a "flat top window". Within the specified frequency range, the FFT bin that has the highest level is searched for; the level of this bin is the maximum level of a single frequency disturbance.
d) The total noise powers obtained from such repeats shall be averaged. The total result shall be 10*log10 of this average in dB.
e) The single frequency maximum powers obtained from such repeats shall be averaged. The total result shall be 10*log10 of this average in dB.
7.3.3 Sending (electrical interface UE)
Same method as in clause 7.3.1.
7.3.4 Receiving (electrical interface UE)
Same method as in clause 7.3.1, except that the idle noise signal is captured at the receive output of the electrical reference interface.